We propose to synthesize a variety of specific analogs of amino acids having alkylating features which will permit them to form covalent bonds with S37 ascites tumor cell amino acid transport systems which we have previously characterized. It is our expectation that many of these analogs will specifically inhibt individual transport systems in an irreversible manner. Radiolabeled analogs will subsequently be employed, using the functional inhibition studies as a guide to appropriate conditions, to tag transport system components in the cell membrane. Following isolation of transport system components they will be studied for binding properties and for enzymatic activities which may be associated with the process of transport of amino acids across the tumor cell membrane.